Method of predicting the approaching stall of an aircraft wing

Abstract

A method of predicting the approaching stall of an aircraft wing which is dependent on an inherent characteristic of the airflow as the stall is approached. The method described uses a hot-wire probe which measures the turbulence of the airflow at a predetermined location on the top surface of the wing. When the turbulence exceeds a threshold, which threshold is dependent on the air-speed, a signal is produced which indicates that a stall is imminent. The method can be particularly applied to an artificial stall warning device fitted to a transport aircraft.

I claim: 
     
       1. A method of predicting the approaching stall of an aircraft wing, comprising: sensing air speed over the wing at a predetermined location spaced above the top surface of the wing to thereby produce input signals representative of air speed fluctuations at said location, said fluctuations being caused by air turbulence over the wing;   using said input signals to produce a signal represensative of a ratio of the air speed fluctuations to an average air speed; and   using said ratio signal to produce a signal indicative of imminent stalling.   
     
     
       2. A method as claimed in claim 1, wherein said location is spaced from the leading edge of the wing by about 66% of the length of a chord of the wing. 
     
     
       3. A method as claimed in claim 1, wherein said location is at a height above the wing which is below 8% of the length of a chord of the wing. 
     
     
       4. A method as claimed in claim 1, wherein said location is at a height above the wing which is between 1% and 4% of the length of a chord of the wing. 
     
     
       5. A method as claimed in claim 1, wherein said signal indicative of immiment stalling is produced when the air turbulence exceeds an air speed dependent threshold, and said using said input signal includes continuously sensing a relationship of the measured air turbulence to said turbulence threshold. 
     
     
       6. A method as claimed in claim 1, wherein said sensing is performed using heated body probe means. 
     
     
       7. A method as claimed in claim 6, wherein said sensing is performed using a hot wire probe. 
     
     
       8. A method of predicting the approaching stall of an aircraft wing, comprising: directly exposing airspeed sensing means to a free airstream over the wing at a predetermined location spaced above the top surface of the wing and above a boundary layer, to thereby produce input signals representative of airspeed fluctuations at said location, said fluctuations being caused by air turbulence over the wing;   using said input signals to produce a signal representative of a ratio of the airspeed fluctuations to an average airspeed; and   using said ratio signal to produce a signal indicative of imminent stalling.   
     
     
       9. A method as claimed in claim 8, wherein said airspeed sensing means is heated body probe means. 
     
     
       10. A method as claimed in claim 8, wherein said location is spaced from the leading edge of the wing by about 66% of the length of a chord of the wing. 
     
     
       11. A method as claimed in claim 8, wherein said location is at a height above the wing which is below 8% of the length of a chord of the wing. 
     
     
       12. A method as claimed in claim 8, wherein said location is at a height above the wing which is between 1% and 4% of the length of a chord of the wing. 
     
     
       13. A method as claimed in claim 9, wherein said airspeed sensing means is a hot wire probe. 
     
     
       14. A method as claimed in claim 8, said signal indicative of imminent stalling is produced when the air turbulence exceeds an air speed dependent threshold, wherein said using said input signals includes continuously sensing a relationship of the measured air turbulence to said turbulence threshold.